ACTION OF WATER ON LEADEN PIPES. 
345 
ly adopted at mints. The same general method has been 
extended by Gay-Lussac to ascertain the strength of alkalies 
and bleaching powder. It is employed with protosulphate 
of iron and subchloride of mercury for the latter purpose. 
It is the method of graduated solutions. 
A gramme of lead in the form of the acetate (common 
sugar of lead,) which contains 3 atoms of water, is dissolved 
in 100 grms. or parts of distilled water. This constitutes 
solution No. 1. 
10 parts of this solution are diluted with 90 parts of water 
to make solution No. 2. 
10 parts of solution No. 2, diluted with 90 parts of water, 
make solution No. 3. 
In the same manner solutions No. 4, No. 5 and No. 6 are 
prepared. 
10 parts of each solution are placed in corresponding 
test-tubes (about six inches long, five-eighths of an inch 
wide, and closed at one end,) and hydrosulphuric acid 
transmitted through them, till the liquid, first blackened by 
the formation of sulphuret of lead, becomes clear. 
Test-tube No. 1 contains one-tenth of a gramme of lead 
in the form of sulphuret — a black powder at the bottom. 
Test-tube No. 2 contains one-hundredth of a gramme. 
No. 3, one-thousandth. 
No. 4, one ten-thousandth. 
No. 5, one hundred-thousandth. 
No. 6 yielded no precipitate without concentration. 
Each succeeding precipitate in the series, setting aside a 
slight allowance io be made on account of solubility, was 
one-tenth as voluminous as the one above. 
Having prepared this scale of quantities, it is required to 
determine the amount of lead in a given diluted solution. 
An experiment is made to ascertain if the quantity be large 
enough to give an immediate precipitate with sulphuret of 
ammonium. This being decided in the negative, 50 cubic 
centimetres or grammes of water (corresponding with 50 
